The main engine of a coiled tubing unit is the injector head. This component contains the mechanism to push and pull the coiled tubing in and out of the hole.
In one aspect, embodiments disclosed herein relate to a system for controlling a coiled tubing injector head, the injector head having a pair of continuous loop drive chains having opposed, elongated parallel runs spaced apart to form a path for engaging tubing passing there through, each drive chain independently driven by a drive motor. The system includes a hydraulic control line in fluid communication with each drive motor, a valve associated with one or both hydraulic control lines, and a sensor associated with each drive motor. Each sensor is configured to output to a digital computer a signal representative of a motor speed, and at least one valve associated with a hydraulic control line is operable to regulate pressure in the hydraulic control line and thereby increase or decrease the speed of the corresponding motor until both speed sensors report substantially matching motor speeds.
In other aspects, embodiments disclosed herein relate to a method for controlling a coiled tubing injector head, the injector head having a pair of continuous loop drive chains having opposed, elongated parallel runs spaced apart to form a path for engaging tubing passing there through, each drive chain independently driven by a motor. The method includes selecting a desired drive motor speed, monitoring sensor outputs associated with each drive motor speed, and operating a valve associated with one or both of the drive motors to increase or decrease hydraulic pressure to a swash plate of one or both of the drive motors until both speed sensors report substantially matching outputs.